Phytosterols and their derivatives hardened by hydrogenation, phytostanols, have been known for many years for their cholesterol-lowering properties. As early as 1991, researchers demonstrated the effectiveness of these substances in inhibiting the absorption of cholesterol in the intestine and through the inner blood vessel walls. Accordingly, sterols and stanols are widely used in the food industry because, through their hypocholesterolemic effect, they minimize future diseases, such as atherosclerosis, heart disease and hypertension. Since phytosterols and stanols are insoluble in water and only poorly soluble in fats and oils, the incorporation of these cholesterol-lowering agents in food preparations, cosmetic or pharmaceutical products poses considerable problems. The unfavorable solubility behavior of the substances results not only in poor dispersibility, but also in reduced bioavailability and in unsatisfactory stability of the food preparations.
Efforts to solve this problem have included the formulation of esters of the sterols, as described in European patent application EP 1275309 A1, or esters of the stanols, as described in U.S. Pat. No. 5,502,045, which had slightly improved processability through their better solubility, but which also showed different hypocholesterolemic activity in relation to the free sterols. However, the esterified derivatives are also not sufficiently soluble to allow simple incorporation.
Numerous patent applications describe how the availability of sterols can be improved by reducing their particle sizes, mainly by micronization. Thus, DE 102 53 111 A1 describes powder-form phytosterol formulations with a mean particle size of 0.01 to 100 μm which are readily redispersible in water. A process for the production of a sterol dispersion, in which the sterols have a particle size distribution of 0.1 to 30 μm, is disclosed in International patent application WO 03/105611 A2.
However, the micronization of the sterol particles is not in itself sufficient to enable satisfactory incorporation into food products. Although the bioavailability of the finely dispersed particles can be improved by increasing the surface area, the micronized particles show poor wetting behavior, readily aggregate, and generally float on the surfaces of aqueous dispersions. In many cases, the ground sterol can only be dispersed in a beverage by special methods involving intensive mixing. However, intensive mixers are not normally available to the end user of the food manufacturers.
Accordingly, many manufacturers combine micronization of the sterols with the additional use of emulsifiers. One example of this are the preparations described in European patent EP 0897671 B1 which contain sterols and sterol esters with a particle size of at most 15 μm in a mixture with emulsifiers, the ratio by weight of emulsifier to sterol in the aqueous phase being less than 1:2. A sterol/emulsifier dispersion disclosed in European patent application EP 1142494 A1 has a particle size distribution of 1 to 40 μm. Commonly used emulsifiers are monoglycerides and polysorbates as disclosed in U.S. Pat. No. 6,623,780 B1, U.S. Pat. No. 6,376,482 B2, WO 02/28204 A1. Even though these emulsifiers are distinguished by high compatibility and have been known for some time as food emulsifiers, efforts are being made to reduce the quantity in which such emulsifiers are used or even to avoid them altogether because emulsifiers also influence the bioavailability of other substances present in the foods or can adversely affect the stability of the formulations.
Avoiding emulsifiers was also the goal of the sterol formulations disclosed in European patent EP 1059851 B1 which contain thickeners for better dispersibility.
Numerous other methods for improving solubility and dispersibility, such as formulating as emulsions, microemulsions, dispersions, suspensions or complexing with cyclodextrins or bile salts, are described in International patent application WO 99/63841 A1, which also mentions formulation in the form of solids dispersions. PEG, PVP, copolymers, cellulose ethers and esters are proposed as carriers.
European patent application EP 1074185 A1 also describes sterol-containing formulations with a matrix which are distinguished by advantageous organoleptic properties of the preparations and which are used for confectionery. However, these formulations are prepared with the addition of water or water and emulsifiers and, accordingly, show reduced stability.
The problem addressed by the present invention was to provide a formulation which would allow the simple and effective dispersion and incorporation of sterols, stanols and esters thereof in foods while reducing or avoiding the use of emulsifiers. The sterol formulation would be readily produced and would be distinguished by high stability in storage.